The present invention relates to apparatus for use in ultrasonic testing and, in particular, to an apparatus for providing a fluid coupling between a piezo-electric crystal transducer element and a test body.
In the inspection of a test body by ultrasonic techniques, ultrasonic waves are generated by the transducer, directed at the test body and reflected therefrom back to the transducer so that the time differential between pulses may be used to ascertain various features of the test body. As can be readily appreciated, it is essential for the ultrasonic energy to be efficiently coupled between the transducer and the test body. One fairly effective but problem-ridden method of providing a coupling comprises interposing a water column between and in intimate contact with both the transmitting-receiving face of the transducer and the surface of the test body. In the past, the means for performing an ultrasonic type of inspection generally included a housing for forming a column of a coupling fluid to flow between the transducer and the workpiece.
A primary area of concern with such a coupling means is that foreign matter becomes accumulated on the operative end of the transducer. In particular, with time in service dirt, e.g., mud, scum and solids, and fine air bubbles become deposited on the flat surface of a transducer during the use of such a system. The material deposited on the surface of the transducer causes a deterioration of the signal which subsequently causes such signal to be lost in the electrical circuit noise caused by the deposits.
Accordingly, it is an object of this invention to provide an ultrasonic testing apparatus which obviates the disadvantageous phenomena reported above and yet enables effective fluid coupling between the transducer and the test body.
It is a further object to provide such a device in which there is an elimination of dirt and air bubbles from the surface of the transducer which permits an accurate testing and inspection of the test body.